Some 4.4 project musings

[Jeff Law]

Andrew MacLeod wrote:
> 
> There are a few things that I'm considering working on for the 4.4 
> release, and I figured I'd see what others thought.  Is anyone 
> considering/doing similar or related work?
> I'll summarize each, and then go into more details.
> 
> 1 - Pass cleanup.  There have been rumblings about this, but I haven't 
> seen a lot of actual progress. We currently run 100's of passes all the 
> time, and we don't really know how effective or necessary many of them 
> are. We also don't know whether the cleanups they run are truly doing 
> much.  It would be nice to do some actual analysis and do something with 
> the results.
[ ... ]


FWIW, this is an area I've always thought we could make some
improvements.  For example, we've got cases where knowing
how pass A changed the IL may allow us to skip pass B.  This
first came up in the context of skipping cse2, but it applies
in the SSA optimizers as well, possibly even more so.

Jeff